Protective surface



Aug. 1,- 1939. A. CRAWFORD l 2,167,972

rnT'EcTIvE SURFACE Filed Aug'. 19, 19574 Patented Aug. 1, 1939v v i i UNITED STATES PATENT oFFlcE PROTECTIVE SURFACE Richard d. Crawford, Akron, Ohio, assigner to The B. F. Goodrich Company, New York, N. Y.,

a corporation of New York Application 'august 1a, i937, serian No. 159,842

n caras. (ci. ctt-1st) This invention relates to protective surfaces, any. small opening in the rubber caused by the and especially tc the protection of surfaces oi discharge or otherwiseisvery detrimental owing rubber articles from the action of sun and oil, to the vulnerability of stretched rubber to rupand also to the provision of electrical conductivity ture once it is broken, even though the originali 5 of the surface despite the dielectric properties ci aperture be small. Rupture is undesirable as t the rubber itself. The invention is applicable esweakening the article and jeopardizing its air-'- pecially to the surfaces of rubber covering structightness and rendering it vulnerable to penetra tures for air foils and'other parts oi aircraft, such, tion by moisture. The provision of electrical confor example, as inflation shoes for ice removal ductivity is useful on other surfaces also, such, for

and rubber. abrasion shoes for the leading edges example, as the surfaces of abrasion shoes of rub1 19 of air foils. The invention is useful also for the ber or other dielectric material for aircraft and protection of other articles, for example. the sideother structures, and also on the sidewalls of walls of tires, where it is desired to provide retires, in which the rubber of the tire owing to sistance to sun-checking and den cracking oi the its high dielectric properties resists the easy disrubber surface, and `to provide electrical concharge cf static accumulation without undesirl@ ductivity for chargesvo static electricity, the able sparking, or penetration of the material, rubber itself being a poor conductor, and also and the provision of aconducting protective coatfor the protection ci surfaces such as metallic ing is sometimes desirable even on the surface of surfaces where surface oxidation oi the imprornetallic articles where oxidation will reduce the tected metal will reduce the electrical conducconductivity.

tivity of the surface. Referring to the embodiment of the invention The chief objects of the invention are to provide illustrated in the drawing, indatable rubber shoe electrical conductivity in the surface; to provide units It, it, and H, I l, are provided at the leading eiectively for resisting the action of oil on the edges of the wings of an airplane l i, and shoe surface; to provide resistance to checking of the units it, it, are provided also at the leading edges 25 surface as a result of exposure tosunlight; and of the stabilizing fins at the tail of the airplane to provide these properties While nevertheless for ice removal. Each unit comprises an envelope maintaining edectiveness oi the protected strucor. cover of stretchable rubber it, which encloses ture for any iiexing or distending function that a plurality of inflatable tubes l5, i5, and which 30 it is intended to perform. ls attached along its edges to the airplane sur- 3@ 55 Yrubber oiftbefshoes .1S mounted; 19 ,12?981911.. and aixnewer These and further objects will be apparent face. The tubes are adapted to be inated for from the following description, reference bein the purpose of changing the surface contour to had to the accompanying drawing of which; break up accumulated ice, in a manner for exam- Fig. l is a perspective view, with parts broken ple as is disclosed in the W. C. Geer Patent No.

away, of an airplane, showing-on .the leading 1,998,809 of April 23, 1935. 35 edges of its Wings and stabilizers inatable shoes Preferably the units have metal fairing strips mounted thereon and.V constructed according to, IG, i6, il, Il, i8, it, extending along the airplane and embodying the invention in its preferred surface at the margins ofthe units. The fairing form. strip may be held in place as by means of metal- Fig. 2 is a vertical section showing the manner lie screws, bolts, or rivets, Ilia, Isa, lla, iia, ita, i0 in which a portion of the shoe structure is as- 18a, extending through the strip unit and skin ci` Sembled; the airfoil in the cases where the latter is of Fig. 3 is a perspective view, with parts broken strong metal, or the attachment may be to the away and sectioned, of the assembled and coated underlying structure of the airfoil.

Surface Covering of the shoe,l The shoe units or portions thereof which are 45 The invention provides, among other things, disposed in the air-stream of the propeller are for conducting away electrical charged which may often subjected -to the depositing of oil on their accumulate upon the' surfaces of-v articles, Asoithat f. surfaces'from the motors, andtheinvention v pro-p y, Ac these fcharges'will not rupture' the material, or# vides.for,oilresistant protectill.59` @he' S111" vz 5G cause sparking such as to ignite fuel,or interfere faces 'so that r.the rubber of ,the ,Shoes willnot 50 with radio operation or. have other-'harmful-efdeteriorate Abecauseof ythe-action of theoil and; feet." AfInfthe. case of inatable'rubbe'r shoesponi. sQ-thattheelectrlc,conductivitymdescribedmore f* aircraft for ice removal, the prevention of such; fullyfhereinaiterfwll kbeIllllailligi.l'lffSfSlethe 4 discharge is 'especially desirable lnasmuchas the presencepoitheoil andthe agitation V,ausedby the,y

For the purpose of providing electrical conductivity to the surface of the shoes,'the rubber itself being undesirably low in such conductivity, especially in a condition of stretch, I provide a surface coating on the rubber that is electrically conductive, even when considerably stretched and at the same time preferably is oil-resisting; that is able to flex and stretch with the rubber Without objectionable cracking and preferably able to contribute to its elasticity; and that is resistantto the action of sunlight. These results may be obtained by the application of a coating material comprising neoprene (polymerized 2-chloro-butadiene) having mixed therewith a substance that is highly conductive to electricity, preferably graphite in finely divided form. Good results haveben obtained with the use of graphite particles of about 2 or 3 microns in size. Only a very thin layer of the neoprene-graphite coating need be applied to obtain the desired results, and this thin coating layer may be conveniently obtained by first providing a liquid dispersion of the neoprene and graphite composition' for spreading. The dispersion may be in the form of either a. solvent cement or an aqueous dispersion.

The following illustrative procedure is well adapted to the obtaining of a suitably thin and uniform coating of the neoprene-graphite composition, and it makes possible the strong union of this surface coating to the underlying rubber structure despite the fact that the neoprene and the rubber are not easily adhered to one another. Upon a suitable support 24 is laid a backing sheet 25 having a smoothsurface. 'Ihis sheet o may be of metal, preferably tinned to provide a smooth, rigid surface. Upon the surface ofthe backing sheet 25 is applied a layer I9 of a suitable lubricating material such. for example, as a suitable soap. Upon this is deposited a layer 2li of the neoprene-graphite dispersion, preferably by' spraying, to provide a thin layer of uniform thickness. This layer may be built up to the desired thickness by applying successive coatings 20a, 20h, 2Ilc, 20d, permitting each coat to dry at least partially before the succeeding coat or coats are applied. A layer 2| of neoprene dispersion Without the graphite may be applied next, and upon this a layer 22 of intermixed neoprene and rubber,`

and a layer 23 of rubber, preferably in sheet form, may then be applied. By this composite structure, after vulcanization, a strong union or anchorage of the layers of the composite structure is provided despite the differences in materials.

A Before vulcanization the tubes I5, I5, and the other parts of the shoe preferably are'assembled upon the layer 23, and the whole, while it is still on the backing sheet 25, is then vulcanized, whereupon it may be stripped from the backing 25. The lubricant I9 facilitates such removal by preventing excessive adhesion of the neoprene-graphite layer 'to the backing 25, and where tinned metal is used for the backing sheet 25, a very smooth surface on the shoe unit results.

I8a, I8a, passing through the strips, shoe and airplane skin, a direct path is provided for charges of electricity from the surface 20 t0 the ,metallic structure of the airplane. L

For the lubricant I9, various substances may be used, such for example as salts of sulphated alcohols, soluble cellulose esters, various soaps, talc, soapstone and waterglass.

While neoprene is preferred as the binder for the highly conductive substance in the layer 20, the neoprene having the advantages of being highly resistant to the action of oil, to sun checking and to ex cracking and of being itself a better electrical conductor than soft rubber, other non-rubber materials having some or all of these characteristics to a suitable degree may be used, such, for example, as plasticized polymerized vinyl chloride, aliphatic polysulphide and plasticized chlorinated rubber. Graphite is preferred as the highly conductive substance in the layer 20, but other conductive substances may be used, such, for example, as metallic powders.

As an illustrative example, the following composition has given good results for the dispersion used to provide the coats of the layer 20:

Neoprene, parts by volume Graphite, 35 parts by volume Softener, 5% by weight of neoprene Vulcanizing and age-resisting ingredients Solvent or aqueous dispersion vehicle The layer 2I may be the same as above, but omitting the graphite.

While it is preferred that the layers 20 and 2| be deposited by spraying, the dispersion may be of a suitable thickness for application for spreading as a paste, if desired. Instead of applying these layers directly on the sheet backing 25, they may be first deposited upon holland cloth or other surface and after the application of the layers y22 and 23, as by calendering, the plied material may be stripped from such surface and applied to the lubricated backing sheet 25. The layer 22 may comprise neoprene and rubber mixed in equal parts by weight with vulcanizing and age-resisting ingredients added. The rubber of the layer 23 may be of the rubber compositions ordinarily employed for the inflatable shoe units. 'I'hese layers may be preliminarily sheeted, as by calendering and may be united by calendering before their incorporation in the composite structure.

As an alternative procedure, the neoprenegraphite composition may be applied directly to the surface of the rubber after the latter has been vulcanized. 'I'he neoprene-graphite lcomposition may be applied to such surface as a dispersion, with either a solvent or aqueous liquid vehicle, by painting, spraying, or by spreading the composition on in the form of a thickened dispersion or paste. Preferably for the sake of obtaining a strong adhesion to the vulcanized rubber body, a tying layer of neoprene-rubber dispersion is applied to the surface of the article before the neoprene-graphite dispersion is applied.

While the invention is especially useful in its application to inflation shoes for ice-removal, it

has utility also in the protection of surfaces of other structures of rubber, such, for example, as o til) abrasion shoes and the side walls of tires, and the invention is useful also for the protection of surfaces of other articles whether they be of rubber. metal, fabrics, or other materials.

Variations may be made without departingiroln the scope of the invention as it is hereinafter claimed.

I claim:

1. Ice-removing apparatus for aircraft including a covering comprising a layer of extensible dielectric material .adapted to be extensively stretched in the operation of said apparatus, and an extensible layer of material at the surface of the dielectric material of relatively great conductivity adapted to be stretched therewith and to be electrically conductive in a condition of stretch.

2. Ice-removing apparatus for aircraft including a covering comprising a layer of rubber adapted to be extensively stretched in the operation of said apparatus, and a layer of extensible neoprene composition upon said rubber and adapted to be stretched therewith, the neoprene layer including electrically conductive graphite and being conductive of electrical charges in a` condition of stretch.

3. Apparatus of the class described comprising resiliently stretchable material subjected to extensive resilient distortion in the operation thereof,

Vand a protective coating therefor comprising neoprene composition and particles of electrically conductive substance upon the surface of said material adapted to b e distorted with said material and to present an electrically conductive surface of the material in its distorted condition.l

4. Apparatus. of the class described comprising rubber composition subjected to extensive resilient distortion in the operation thereof, a protective coating therefor comprising neoprene composition and graphite upon the surface of said rubber composition adapted to be distorted with'the rubber composition and to be electrically conduc- Y charges, said coating comprising neoprene composition and graphite particles upon the surface of said rubber composition, the neoprene of said coating being effective to maintain protection to the rubber and electrical conductivity between the particles of graphiteseparated by the distortion of the coating.

6. Apparatus exposed to contact with oil comprising an oil-resisting surface layer including` neoprene composition and an electrically conductive material in the neoprene layer for electrical conductivity of said layer. Y i

7. Apparatus exposed to contact with oil and to A|55 uid currents at high velocity comprising a body of rubber composition and an oil-resisting surface layer of neoprene composition and graphite particles dispersed in the neoprene layer for electrical conductivity of said layer.

'8. Article of the class described comprising a layer of resilient, stretchable material adapted to be distorted, a protective coating on the surface thereof comprising, stretchable non-rubber but rubber-like material highly resistant to the action of sunlight and including particles of electrically conductive substance permitting distortion of the material and providing electrical conductivity of the surface in the distorted condition of the material, and an intermediate thin layer of stretchable lbinding material securing the protective coating to the underlying layer.

9. Article of the class described comprising a layer of resilient, stretchable material adapted to be distorted, a protective coating on the surface extensively distorted in the use thereof, said ar-l ticle comprising a layer of resilient 'rubber material and a protective coating on the surface thereof comprising a thin layer of non-rubber but stretchable rubber-like composition highlyl resistant to the action of sunlight and including particles of electrically conductive substance, said coating permitting extensive distortion of the article while maintaining'electrical conductivity of the surface thereof in its distorted condition.

p 11. Article of the class described adapted to be Y extensively stretched in the use thereof, said article comprising a layer of resilient stretchable material and a protective coating on the surface thereof comprising a thin layer of stretchable non-rubber but rubber-like composition highly resistant to the action of sunlight and including particles of electrically conductive substance, Asaid coating permitting stretching of the article while maintaining electrical conductivity of the surface thereof in its stretched condition.

RICHARD A. CRAWFORD. 

